pgsql: Allow json{b}_strip_nulls to remove null array elements

Allow json{b}_strip_nulls to remove null array elements

An additional paramater ("strip_in_arrays") is added to these functions.
It defaults to false. If true, then null array elements are removed as
well as null valued object fields. JSON that just consists of a single
null is not affected.

Author: Florents Tselai <florents(dot)tselai(at)gmail(dot)com>

Discussion: https://postgr.es/m/4BCECCD5-4F40-4313-9E98-9E16BEB0B01D@gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4603903d294bbdd644afecf9b5970827db6d1ff5

Modified Files
--------------
doc/src/sgml/func.sgml | 17 +++++++----
src/backend/catalog/system_functions.sql | 14 +++++++++
src/backend/utils/adt/jsonfuncs.c | 27 +++++++++++++++--
src/include/catalog/pg_proc.dat | 4 +--
src/test/regress/expected/json.out | 50 ++++++++++++++++++++++++++++++++
src/test/regress/expected/jsonb.out | 50 ++++++++++++++++++++++++++++++++
src/test/regress/sql/json.sql | 19 ++++++++++++
src/test/regress/sql/jsonb.sql | 18 ++++++++++++
8 files changed, 190 insertions(+), 9 deletions(-)